Hearing Aid Gain Control for Comb Filter Artifact Reduction
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Solution Overview
Problem
Hearing aids often produce nonlinear artifacts due to the superposition of unprocessed ambient sound and processed output sound, leading to discomfort and reduced intelligibility, especially when comb filter artifacts occur, which are difficult to predict and manage.
Innovation Solution
A method that adjusts the amplitude of output sound based on the ratio between unprocessed ambient sound and processed sound within specific frequency bands, using transfer functions to minimize the formation of comb filter artifacts by altering the gain factor when the ratio falls outside predefined limits, thereby reducing hardware complexity and computational intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If frequencies likely to cause comb filter artifacts are consistently attenuated, then comb filter artifacts are reduced, but noise reduction algorithms become unavailable and hearing aid benefit is reduced
Solution Approach 1:
The hearing aid dynamically adjusts the amplification of frequency bands based on the detected ratio between unprocessed ambient sound and processed output sound. When the ratio indicates a high probability of comb filter artifacts, the amplification is reduced; otherwise, normal amplification and noise reduction algorithms are applied. This dynamic adaptation resolves the contradiction by making the system flexible rather than statically attenuating frequencies.
Solution Approach 2:
The system changes the amplification parameter (gain factor) for specific frequency bands based on the calculated ratio between ambient and processed sound. By adjusting this parameter conditionally, the system reduces comb filter artifacts only when necessary, preserving the effectiveness of noise reduction algorithms in other conditions.
2Object-affected harmful factors
If amplitude is adjusted based on estimated superposition, then comb filter artifacts are reduced, but computational intensity increases and errors may occur
Solution Approach 1:
The patent extracts only the essential information needed for artifact reduction by directly measuring the ratio between unprocessed ambient sound and processed output sound using microphones and transfer functions, rather than performing full superposition estimation. This extraction approach reduces computational intensity while maintaining effectiveness in reducing comb filter artifacts.
3Reliability
If frequency-specific amplification is applied according to hearing loss, then hearing aid effectiveness is improved, but comb filter artifacts increase due to nonlinear superposition
Solution Approach 1:
The system dynamically adjusts the frequency-specific amplification based on the detected ratio between ambient and processed sound. When the ratio falls within a critical range that would cause comb filter artifacts, the amplification is temporarily reduced. This dynamic adjustment maintains hearing aid effectiveness while preventing artifacts, resolving the contradiction between reliability and harmful factors.
Solution Approach 2:
The system takes preliminary action by detecting the ratio between ambient and processed sound and preemptively adjusting amplification before comb filter artifacts can occur. This prevents the nonlinear superposition effects while maintaining hearing aid effectiveness in normal conditions.
Data Source
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AI summary
The invention relates to a method (24) for operating a hearing aid (2) in which an input signal (16) is generated by means of a microphone (6) based on ambient sound (7). Based on the input signal (16), an output signal (18) is provided, and an output sound (22) is emitted by means of a receiver (10) based on the output signal (18). The unprocessed ambient sound (22) present in the vicinity of the receiver (10) is determined, and the ratio (36) between the unprocessed ambient sound (22) and the output sound (12) is determined for different frequency bands. The amplitude of the output signal (18) for the frequency band is varied, whereby the ratio (36) lies between an upper limit (38) and a lower limit (40). The invention further relates to a hearing aid (2).